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Comparison of Subtalar Joint Range of Motion and Dorsiflexor Muscle Activity Between Normal and Pes Planus Feet
J Korean Soc Phys Med 2018;13(2):129-135
Published online May 31, 2018;
© 2018 Korean Society of Physical Medicine.

Eun-Kyung Koh, PT⋅Do-Young Jung, PT1†

Department of Physical Therapy, Masan University
1Department of Physical Therapy, Kinesiopathologic Science Institute, Joongbu University
Received April 19, 2018; Revised April 20, 2018; Accepted April 24, 2018.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
PURPOSE: The imbalance of pretibial muscles can be a factor contributing to the development of pes planus. However, no study has yet compared the muscle activity of the tibials anterior (TA) to that of the extensor digitorum longus (EDL). The purpose of this study was to determine whether there are differences in the electromyographic (EMG) TA and EDL amplitude indexes (AIs) between normal and pes planus feet.
METHODS: A total of 14 subjects with normal feet and 15 subjects with bilateral pes planus participated in this study. TA and EDL muscle activities were measured using a wireless EMG system and the angles of ankle dorsiflexion and eversion of the subtalar joint were measured using a universal goniometer during active ankle dorsiflexion in the prone position. AI was calculated as follows: amplitudeTA‒amplitudeEDL / (amplitudeTA+amplitudeEDL) / 2×100.
RESULTS: The AIs of the TA and EDL were significantly lower in pes planus feet than in normal feet (p<.05). The angle of subtalar eversion was significantly greater in pes planus feet than in normal feet during active ankle dorsiflexon (p<.05). However, there was no significant difference in the angle of ankle dorsiflexion between normal feet and pes planus feet (p>.05).
CONCLUSION: This study showed that TA muscle activation was lower in pes planus feet than in normal feet, resulting from greater eversion range of motion during active ankle dorsiflexion. We suggest that the imbalance of ankle dorsiflexors must be considered in pes planus management.
Keywords : Extensor digitorum longus, Pes planus, Pronation, Subtalar joint, Tibialis anterior

May 2018, 13 (2)
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